When constituting a cell forming a communication area in a mobile communication network, even when a mobile terminal is not present in the cell, the base station continuously sends out radio waves to indicate the presence of the cell to the mobile terminal. For this reason, even in a non-communication state, power is constantly consumed.
For this reason, there has been conventionally proposed an overlay configuration, in which a plurality of small cells are arranged in a macro cell. When a small cell is not communicating, the power consumption of the small cell is reduced to so that power is saved, and the number of small cells is increased so that power is saved while maintaining the traffic capacity.
In this case, a macro cell is provided for indicating the presence of the area to the mobile terminal. For activating each of the small cells, position information is used, which may be obtained by GPS (Global Positioning System) of the mobile terminal. The position information of the cover area of each small cell is compared with the position information of the mobile terminal, and a small cell having a cover area including the position of the mobile terminal, is determined to be the small cell to be activated.
Incidentally, a second base station device, which performs communication processes for wireless signals for a second cell that is arranged redundantly in a first cell, stops receiving at least some of the power, in response to the disappearance of traffic in the second cell. A first base station device corresponding to a first cell, which has received a connection request from a mobile terminal device present in the first cell, identifies a second base station device capable of processing communications for the mobile terminal device. The first base station device selectively resumes the receiving of power for the identified second base station device. The above technology has been proposed (see, for example, Patent Document 1).
Furthermore, there is proposed an upper-layer base station including an upper-layer wireless unit that implements communications with a wireless terminal present in an upper-layer cell; an inter-upper-layer base station communication unit that implements communications with a lower-layer base station forming a lower-layer cell; and an upper-layer control unit that gives an instruction to a lower-layer base station that satisfies a communication connection condition with respect to a wireless terminal with which communication is presently performed, to switch from a power saving mode to a regular operation mode, via the inter-upper-layer base station communication unit (see, for example, Patent Document 2).
Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-91748
Patent Document 2: Japanese Laid-Open Patent Publication No. 2011-130260
In the conventional technology, for activating a small cell, the position information of the mobile terminal and the position information of the cover area of the small cell are used, and therefore the following problem arises. An optimum communication quality is not necessarily secured only by the relationship between the position of the mobile terminal and the position of the small cell. For example, even when the position of the mobile terminal is in the cover area of the small cell, there are cases where communication is not possible due to building shadows. Therefore, there may be cases where communication is not possible at the stage of actually attempting to perform communication. Furthermore, in order to associate the position of the mobile terminal with the cover area of the small cell, a database of position information needs to be constructed, which leads to an increase in cost.